In many applications, data are sensed at various locations around a network. In such applications, the data must often be tagged with timing information. This timing information should be consistent across the network. For example, in exploring for oil, an area may be surveyed using sensors (accelerometers) disposed in a grid. Seismic shocks are induced by triggers such as explosives or vibrator trucks, and in response the sensors provide data indicative of soil content and condition. This data must be time-stamped so it can be synchronized across the network. Clocks at the sensors may be used to time-stamp the data.